Emerging Copper-Based Semiconducting Materials for Photocathodic Applications in Solar Driven Water Splitting

Hydrogen production through solar-driven water splitting is a promising approach and an alternative to the conventional steam reforming of natural gas and coal gasification. The growing energy demand and environmental degradation through carbon-emitting fossil fuels urge a transition in the usage of non-renewable to renewable sources of energy. The photocathodes in a photoelectrochemical (PEC) water-splitting cell are essential for the direct evolution of hydrogen. Among the known photocathodes, Cu-based p-type semiconducting materials are the most promising photo-absorber materials owing to their low-cost, low toxicity, natural abundance, suitable bandgaps, and favorable band edges for reduction. Moreover, the chemical stability and the rate of recombination significantly limit the longevity, the PEC performance, and practical applicability of Cu-based photocathodes. To overcome these problems, it is critical to have a thorough understanding of the constraints, improvement strategies, and an assessment of current developments in order to construct and design highly stable and efficient photocathodes. Here, in this review we have summarized the development of Cu-based metal oxide and sulfide photocathodes with the significant operational challenges and strategies that have successfully been employed to enhance the PEC performance. Furthermore, the emphasis is placed on recent reports and future perspectives regarding emerging challenges

Recent trends in photoelectrochemical water splitting: the role of cocatalysts

Environmental degradation due to the carbon emissions from burning fossil fuels has triggered the need for sustainable and renewable energy. Hydrogen has the potential to meet the global energy requirement due to its high energy density; moreover, it is also clean burning. Photoelectrochemical (PEC) water splitting is a method that generates hydrogen from water by using solar radiation. Despite the advantages of PEC water splitting, its applications are limited by poor efficiency due to the recombination of charge carriers, high overpotential, and sluggish reaction kinetics. The synergistic effect of using different strategies with cocatalyst decoration is promising to enhance efficiency and stability. Transition metal-based cocatalysts are known to improve PEC efficiency by reducing the barrier to charge transfer. Recent developments in novel cocatalyst design have led to significant advances in the fundamental understanding of improved reaction kinetics and the mechanism of hydrogen evolution. To highlight key important advances in the understanding of surface reactions, this review provides a detailed outline of very recent reports on novel PEC system design engineering with cocatalysts. More importantly, the role of cocatalysts in surface passivation and photovoltage, and photocurrent enhancement are highlighted. Finally, some challenges and potential opportunities for designing efficient cocatalysts are discussed

Integrated p-n Junctions for Efficient Solar Water Splitting upon TiO2/CdS/BiSbS3 Ternary Hybrids for Improved Hydrogen Evolution and Mechanistic Insights

The development of efficient and novel p-n heterojunctions for photoelectrochemical (PEC) water splitting is still a challenging problem. We have demonstrated the complementary nature of (p-type) BiSbS3 as a sensitizer when coupled with (n-type) TiO2/CdS to improve the photocatalytic activity and solar to hydrogen conversion efficiency. The as-prepared p-n heterojunction TiO2/CdS/BiSbS3 exhibits good visible light harvesting capacity and high charge separation over the binary heterojunction, which are confirmed by photoluminescence (PL) and electrical impedance spectroscopy (EIS). The ternary heterojunction produces higher H-2 than the binary systems TiO2/CdS and TiO2/BiSbS3. This ternary heterojunction system displayed the highest photocurrent density of 5 mA center dot cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE) in neutral conditions, and STH of 3.8% at 0.52 V vs. RHE is observed. The improved photocatalytic response was due to the favorable energy band positions of CdS and BiSbS3. This study highlights the p-n junction made up of TiO2/CdS/BiSbS3, which promises efficient charge formation, separation, and suppression of charge recombination for improved PEC water splitting efficiency. Further, no appreciable loss of activity was observed for the photoanode over 2500 s. Band alignment and interfaces mechanisms have been studied as well

Plasmonic nanometal decorated photoanodes for efficient photoelectrochemical water splitting

Plasmonic metal nanoparticles containing photoanodes are known to exhibit stable photoelectrochemical (PEC) performance due to their optical and electronic properties. In this work, we report the application of plasmonic Bi nanoparticles supported over a g-C3N4/Bi2S3 photoanode for PEC water splitting. Typical results indicated that g-C3N4/Bi2S3/BiNPs ternary composite photoanode showed a high photo-current density of 7.11 mA cm−2 at 1.23 V under solar irradiation, which was ∼ 5 and 10 times higher than g-C3N4/Bi2S3 and g-C3N4 photoanodes, respectively. Further, the composite electrode also demonstrated superior solar to hydrogen efficiency and long-term stability. It was concluded that Bi nanoparticles play a major role in enhancing the PEC performance for hydrogen evolution reaction. Thus, g-C3N4/Bi2S3/BiNPs has superior PEC performance and proved to work as an alternative to noble metal based photo-electrodes for solar-water splitting reactions

Influence of Bi–Cu microstructure on the photoelectrochemical performance of BiVO4 photoanode for efficient water splitting

To date, photoanodes containing bimetallic alloy nanoparticles (ANPs) are exposed good photoelectrochemical (PEC) performance for hydrogen production owing to their optoelectronic properties. In this work, low-cost, visible light active and environmental-friendly BiVO4/Bi–Cu nanocomposite photoanode is fabricated via organic decomposition and electrodeposition process. Transmission electron microscope images reveals that Bi–Cu ANPs are uniformly distributed on BiVO4 which can enhance the PEC performance. Typical results originate that BiVO4/Bi–Cu nanocomposite exhibits a high photocurrent density of 10.31 mA cm−2 at 1.23 V and solar-to-hydrogen conversion efficiency of 3.55%, which is higher than other electrodes. In addition, this composite shows excellent long-term stability over 5 h and low charge transfer resistance. These results suggest the introduction of Bi–Cu ANPs enhances the broadband light absorption of BiVO4 due to the excitation of localized surface plasmons at different wavelengths and also improves the charge transportation in the photoanode. Thus, BiVO4/Bi–Cu photoelectrode reports here is superior PEC performance for hydrogen generation providing an economical and feasible route to fabricate surface plasmon resonance (SPR)-enhanced composites as photocatalysts using earth-abundant Bi and Cu metals instead of noble-metals. © 2021 Elsevier B.V

TiO2 Photoanodes Sensitized with Bi2Se3 Nanoflowers for Visible–Near-Infrared Photoelectrochemical Water Splitting

Semiconducting photoelectrodes emerge as an efficient platform for converting light energy into hydrogen by photoelectrochemical (PEC) water splitting. The present study reports the improvement in PEC performance using metal oxide photoelectrodes sensitized with a narrow-band-gap semiconductor Bi2Se3, which extends the light response beyond the visible region and generates and transports charge carriers. When Bi2Se3 nanoflowers (NFs) were incorporated into the TiO2 electrode, the extent of hydrogen production was found to be increased by an order of magnitude. The binary electrode TiO2/Bi2Se3 nanocomposite exhibited a decent photocurrent density of 1.76 mA cm-2 at 1.23 V, which is three times superior to that of pure Bi2Se3 NFs. Moreover, the binary TiO2/Bi2Se3 electrode delivers the highest solar-to-hydrogen conversion efficiency of 1.01% at 0.6 V and incident photon-to-current conversion efficiency of 10.5%. Furthermore, both Bi2Se3 and TiO2/Bi2Se3 electrodes show superior photostabilities for over 6 h. The enhanced PEC activity is attributable to the facile transportation of photoelectrons from Bi2Se3 to TiO2 electrodes, thereby minimizing the charge recombination

Emerging materials for plasmon-assisted photoelectrochemical water splitting

In genomewide association study (GWAS) of a complex phenotype, a large number of variants, many with small effect sizes, are found to contribute to the variability of the phenotype. Subsequent to the identification of such variants in a GWAS, it is of interest to estimate the risk jointly conferred by the variants. We propose three different strategies of combining the risk SNPs to calculate an allele dosage score. Using simulations, we evaluate the different measures of allele dosage score with respect to the risk prediction accuracy of a binary trait and the proportion of variance explained for a quantitative trait. For a binary trait, an allele dosage score defined based on log odds ratio performs marginally better than the other two measures. For a quantitative trait, the measure based on the standardized slope coefficient in linear regression of the trait on single-nucleotide polymorphism (SNP) genotypes performs better than the measures using the weights proportional to log P-value and the proportion of variance explained. We demonstrate the utility of these measures using a real data on type 2 diabetes and fasting blood sugar level in a south Indian population. © 2022, Indian Academy of Sciences

Increased Plasma Concentrations of Cytoskeletal and Ca2+-Binding Proteins and Their Peptides in Psoriasis Patients

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Decoration of plasmonic Cu nanoparticles on WO3/Bi2S3 QDs heterojunction for enhanced photoelectrochemical water splitting

We report a WO3/Cu/Bi2S3 wherein incorporation of Cu nanoparticles (Cu NPs) to enhance the photoelectrochemical activity over WO3/Bi2S3. Cu NPs effectively harvest the light energy upon plasmon excitation and transfer the energy to contacted WO3, thereby improving the photoelectrochemical (PEC) performance. The WO3/Cu/Bi2S3 composite was characterized by scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD) to analyze the morphology and interfacial contact between the semiconductors. The photocurrent density and Solar-to-Hydrogen conversion efficiency for this composite is 10.6 mA cm−2 at 1.23 V (versus RHE) and 3.21% at 0.81 V (versus RHE), which are much higher than WO3/Bi2S3 with 4.02 mA cm−2 at 1.23 V (versus RHE) and 2.46% at 0.81 V (versus RHE) respectively. Moreover, the stability and photo-response of WO3/Cu/Bi2S3 were carried out through chronoamperometric studies. The composite retained its stability over 50 cycles without decay in PEC performance. High incident photon conversion efficiency (IPCE) value of about 51% is achieved which is evident from the high photocurrent density. Incorporation of Cu NPs increase the photoactivity which is evident from the photocurrent value. The increased activity of Cu NPs sandwiched composite is attributed for the quick electron transfer to semiconductor due to surface plasmon resonance (SPR) effect